Detailed explanation of graphics functions in C++

Detailed explanation of graphic functions in C

Graphic functions are a very important and commonly used part of C programming. They can realize the drawing and rendering of various graphics in the graphical interface. Display and interaction functions. This article will introduce in detail the commonly used graphics functions in C and give some sample codes to illustrate their use.

1. Graphics function library

In C, there are many choices for commonly used graphics function libraries, such as Windows API, OpenGL, SFML, etc. Each graphics function library has its own characteristics and uses. Developers can choose a suitable library for development based on project needs. This article focuses on the graphics functions in the Windows API.

2. Window creation and message processing

The basic steps to create a window using Windows API are as follows:

(1) Define a window class and give Window properties and message handling functions.

(2) Register the window class and tell the operating system the existence of the window class.

(3) Create a window and specify the window class and window style.

(4) Enter the message loop and process window messages.

The window class is defined as follows:

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    // 窗口消息处理函数
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    // 创建窗口

    MSG msg;
    BOOL bRet;
    while((bRet = GetMessage(&msg, NULL, 0, 0)) != 0)
    {
        if(bRet == -1)
        {
            // 消息获取失败
            break;
        }
        else
        {
            TranslateMessage(&msg); 
            DispatchMessage(&msg);
        }
    }
    
    return msg.wParam;
}

3. Graphics drawing

Windows API provides some functions for drawing graphics, such as drawing line segments and rectangles , ellipse, etc. The following are some commonly used drawing functions and sample codes:

(1) Draw a line segment

void DrawLine(HDC hdc, int x1, int y1, int x2, int y2)
{
    MoveToEx(hdc, x1, y1, NULL);
    LineTo(hdc, x2, y2);
}

(2) Draw a rectangle

void DrawRect(HDC hdc, int left, int top, int right, int bottom)
{
    Rectangle(hdc, left, top, right, bottom);
}

(3) Draw an ellipse

void DrawEllipse(HDC hdc, int left, int top, int right, int bottom)
{
    Ellipse(hdc, left, top, right, bottom);
}

The above are the basic functions for drawing graphics. Developers can call these functions to draw graphics as needed.

4. Graphic display

Graphics functions can display graphics through the device context (Device Context, referred to as DC). In the window message processing function, graphics can be displayed by obtaining the DC of the window. The following is a sample code:

case WM_PAINT:
    {
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hWnd, &ps);
        
        // 在hdc上进行图形绘制
        
        EndPaint(hWnd, &ps);
    }
    break;

After drawing graphics on hdc, you can end the drawing by calling the EndPaint function.

5. Graphic interaction

Graphic functions can realize interactive operations in the graphical interface, such as mouse clicks, keyboard keys, etc. In the window message processing function, corresponding interactive operations can be realized by judging the message type. The following is a sample code:

case WM_LBUTTONDOWN:
    {
        int xPos = GET_X_LPARAM(lParam);
        int yPos = GET_Y_LPARAM(lParam);
        
        // 鼠标左键点击处理代码
        
    }
    break;

By judging the message type, developers can implement different interactive operations as needed.

6. Summary

This article introduces the commonly used graphics functions in C in detail, and gives some sample codes to illustrate their use. Graphics functions are a very important and commonly used part of C programming. By using graphics functions, developers can implement functions such as drawing, displaying and interacting with various graphics, making the program more vivid and easier to use. I hope this article can be helpful to readers and deepen their understanding and application of C graphics programming.

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